IB Environmental systems and societies 6.2C Climate Models Notes

Long-Term Climate Data: Instrumental and Satellite Records Feed and Validate Climate Models

1. Weather stations, observatories, satellites and radar provide decades to centuries of climate data.
2. Recorded variables include air temperature, precipitation, pressure, wind speed, humidity and GHG concentrations.
3. Long-term records let scientists separate genuine climate trends from short-term variability.
4. These data calibrate, validate and improve climate models and inform mitigation and adaptation decisions.

Direct Measurements: Instrumental Records Are Accurate but Short

1. Standardised instruments in weather stations and observatories give high accuracy and high temporal resolution (hourly to monthly).
2. Consistent instrumental records only extend back to the late 19th to early 20th century, about 150 years.
3. Key direct measurements and their instruments:
   1. Temperature (thermometers, automated sensors).
   2. Rainfall and humidity (rain gauges, hygrometers).
   3. CO₂ (non-dispersive infrared sensors); methane and nitrous oxide (gas chromatography).
   4. Wind speed and direction (anemometers).
   5. Atmospheric pressure (barometers).
   6. Ocean temperature and salinity (buoys and ARGO floats).

Remote Sensing: Satellites Give Global, Repeated Coverage

1. Satellites record large-scale variables with global coverage, including remote oceans, mountains and polar regions.
2. Repeated passes build multi-decade climate datasets.
3. Two sensor types collect the data:
   1. Passive sensors detect solar radiation reflected from Earth's surface.
   2. Active sensors emit their own signal, such as radar, and detect the reflection.
4. What satellites measure:
   1. Sea surface temperatures.
   2. Sea-level rise (satellite altimetry).
   3. Land-use change and deforestation.
   4. Glacial mass and ice-sheet movement.
   5. Aerosol concentration.
   6. Cloud cover and thickness.
   7. Thermal infrared radiation from Earth's surface.

Proxy Records: Models Are Validated Against Deep-Time Evidence

1. Models are calibrated and validated against proxy records that extend climate back hundreds to hundreds of thousands of years, far beyond instrumental data.
2. Key proxies are ice cores, tree rings and sediment or peat cores.

Paleoclimate proxy evidence is covered in detail in 6.2A.

Global Climate Models: Equations on a 3D Grid Project Future Climate